EP0953654B1 - Process and apparatus for gas carburising - Google Patents

Process and apparatus for gas carburising Download PDF

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Publication number
EP0953654B1
EP0953654B1 EP99108094A EP99108094A EP0953654B1 EP 0953654 B1 EP0953654 B1 EP 0953654B1 EP 99108094 A EP99108094 A EP 99108094A EP 99108094 A EP99108094 A EP 99108094A EP 0953654 B1 EP0953654 B1 EP 0953654B1
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EP
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Prior art keywords
ethanol
carbon dioxide
atmosphere
furnace
carbon
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EP99108094A
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German (de)
French (fr)
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EP0953654A1 (en
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Alexander Dipl.-Ing. Jurmann
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Linde GmbH
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Linde GmbH
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising

Definitions

  • the invention relates to a method for carburizing metallic workpieces in a furnace at high temperatures and in an atmosphere containing CO and H 2 , in which the atmosphere is formed by reacting an oxygen-containing hydrocarbon medium, in particular an alcohol, with carbon dioxide.
  • the invention proposes that the atmosphere is formed on the basis of ethanol and carbon dioxide and the anoder Depletion of the atmosphere, i.e. the setting of a certain carbon level, by adjusting the stoichiometric ratio accordingly of ethanol and carbon dioxide.
  • this primarily results in an atmosphere formation reaction in accordance with C 2 H 5 OH + CO 2 ---> 3 CO + 3 H 2 .
  • the accumulation or reaction of the water and carbon dioxide formed during the carburizing process which is usually achieved by CH 4 or C 3 H 8 , is achieved according to the invention by adjusting the stoichiometric ratio of ethanol and carbon dioxide, because if there is an excess supply of ethanol, 2 C 2 H 5 OH + 1 CO 2 ---> CH 4 + 2 CO + 2 CO + 4 H 2 also a methane content in the product gas, which takes over the task of the enrichment gas, which is otherwise supplied independently.
  • the preparation of an enrichment gas is therefore not necessary in the method according to the invention.
  • an atmospheric gas with a CO to H 2 ratio of exactly 1: 1 is produced, which primarily serves to accelerate carburization.
  • the ethanol-carbon dioxide system with regard to its reaction properties offers favorable conditions. It already reacts at about 800 ° C in the desired way and ethanol and carbon dioxide can therefore - according a preferred process variant - for atmospheric formation without further measures directly into a carburizing furnace. A procedure with a standalone atmosphere generator can still work in some Applications may be required.
  • the "ethanol and carbon dioxide" system also results in a two-component system, that is comparatively easy to regulate.
  • the procedure is such that the carbon level in the carburizing furnace is measured continuously and the adjustment of the stoichiometric ratio of ethanol and changing carbon dioxide according to the desired carbon level.
  • Atmospheric formation one component is constantly fed into the system, and the other, depending on a carbon level measurement, supplied in a controlled manner becomes.
  • a carburizing plant according to the invention is specified in claim 1 and is characterized in that the associated carburizing furnace for the purpose of atmosphere formation only an ethanol source (A) and a carbon dioxide source (C) served and therefore with this is connected, and that a measuring device (M) for measuring the carbon level is present in the furnace, which in turn has a quantity control unit in the ethanol feed line and / or the carbon dioxide feed line is connected.
  • the invention is explained in more detail below in connection with the attached figure using an exemplary embodiment.
  • the figure shows a system design according to the invention with regulated CO 2 supply.
  • a carburizing furnace O is first to be coupled to an ethanol source A and to a carbon dioxide source C via suitable lines and actuators.
  • the ethanol supply consists of an ethanol pump P and a line 1, which opens into a atomization unit V before reaching the carburizing furnace.
  • a carbon dioxide feed line 2d likewise opens into the atomization unit.
  • the carbon dioxide feed line 2d divides upstream of the atomization unit V into a parallel circuit section with two lines 2b and 2c, in each of which an actuator - S1 and S2 - is provided for quantity control.
  • the parallel connection is connected to the CO 2 source C via a line section 2a and a main valve H.
  • the carburizing furnace O is equipped with a measuring device M for measuring the carbon level in its interior.
  • the measuring device M in turn is connected to a control device S, which in turn acts on the actuator S2 in the bypass line 2c of the parallel connection.
  • a procedure according to the invention of this system is that the starting media ethanol and carbon dioxide are introduced in certain basic quantities into the furnace O which is at a temperature and which are determined by suitable adjustment of the pumping power of the ethanol pump P and of the actuator S1.
  • the feed quantities are to be adjusted so that one mole of ethanol comes to one mole of CO 2 , with an excess of ethanol generally being provided in the variant shown.
  • an atmosphere is obtained from these starting media, essentially containing 1: 1 CO and H 2 , the carbon level of which is determined by the measuring device M, for example an oxygen probe or a C-flow probe. Since in the described case, in principle an excess of ethanol is used, a relatively high C level arises in the basic setting of the system.
  • the correspondingly programmed control device S triggers the opening of the actuator S2 and thus increases the CO 2 supply. As a result, the C level drops until, when a lower limit to be defined is reached, actuator S2 is closed again. In this way, a relatively simple, extremely efficient, C-level controlled carburizing atmosphere is obtained.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Treating Waste Gases (AREA)

Abstract

The atmosphere used in carburisation of workpieces is based on ethanol and carbon dioxide. Enrichment and depletion of the atmosphere is produced by the corresponding adjustment of the stoichiometric ratio of ethanol and carbon dioxide. An Independent claim is also included for a carburisation apparatus comprising an ethanol source (A) and a carbon dioxide source (C) connected together. A measuring device (M) is also present to measure the carbon level in the furnace.

Description

Die Erfindung betrifft ein Verfahren zur Aufkohlung metallischer Werkstücke in einem Ofen unter hohen Temperaturen und in einer CO und H2 enthaltenden Atmosphäre, bei dem die Atmosphäre durch Umsetzung eines sauerstoffhaltigen Kohlenwasserstoffmediums, insbesondere eines Alkohols, mit Kohlendioxid gebildet wird.The invention relates to a method for carburizing metallic workpieces in a furnace at high temperatures and in an atmosphere containing CO and H 2 , in which the atmosphere is formed by reacting an oxygen-containing hydrocarbon medium, in particular an alcohol, with carbon dioxide.

Es ist aus der DE-PS 43 40 060 ein Verfahren zur Aufkohlung metallischer Werkstücke in einem Ofen unter hohen Temperaturen und in einer CO und H2 enthaltenden Atmosphäre bekannt, bei dem die Atmosphäre zumindest zu Beginn der Aufkohlung auf der Basis eines dem Ofen zugeführten Alkohols und Kohlendioxid gebildet wird, wobei zusätzlich auch ein Anreicherungsmittel zur Einstellung eines bestimmten Kohlenstoffpegels und teilweise auch zur Atmosphärenbildung einzubringen ist. Mit diesem Verfahren kann eine stickstofffreie Aufkohlungsatmosphäre mit einem CO-zu-H2-Verhältnisses von etwa 1:1 und damit sehr guten Aufkohlungseigenschaften erzielt werden. Nachteilig bei diesem Verfahren sind die relativ komplizierten Regel- oder Steuerprozesse für die drei zugehörigen Medien, worin auch die Problemstellung der vorliegenden Erfindung bestand.It is known from DE-PS 43 40 060 a method for carburizing metallic workpieces in a furnace at high temperatures and in an atmosphere containing CO and H 2 , in which the atmosphere at least at the beginning of the carburization on the basis of an alcohol supplied to the furnace and carbon dioxide is formed, an enrichment agent for adjusting a certain carbon level and in some cases also for atmospheric formation also having to be introduced. With this process, a nitrogen-free carburizing atmosphere with a CO to H 2 ratio of about 1: 1 and thus very good carburizing properties can be achieved. A disadvantage of this method is the relatively complicated regulation or control processes for the three associated media, which was also the problem with the present invention.

Zur Lösung dieses Problems wird erfindungsgemäß vorgeschlagen, daß die Atmosphäre auf der Basis von Äthanol und Kohlendioxid gebildet wird und die Anoder Abreicherung der Atmosphäre, also die Einstellung eines bestimmten Kohlenstoffpegels, durch entsprechende Verstellung des stöchiometrischen Verhältnisses von Äthanol und Kohlendioxid erzielt wird.To solve this problem, the invention proposes that the atmosphere is formed on the basis of ethanol and carbon dioxide and the anoder Depletion of the atmosphere, i.e. the setting of a certain carbon level, by adjusting the stoichiometric ratio accordingly of ethanol and carbon dioxide.

Erfindungsgemäß ergibt sich somit in erster Linie eine Atmosphärenbildungsreaktion gemäß C2H5OH + CO2 ---> 3 CO + 3 H2 . According to the invention, this primarily results in an atmosphere formation reaction in accordance with C 2 H 5 OH + CO 2 ---> 3 CO + 3 H 2 .

Es wird also eine Atmosphäre mit einem CO-zu-H2-Verhältnis von 1:1 erzielt, also dem für Aufkohlungen optimalen Verhältnis, das eine maximale Kohlenstoffübergangszahl β zur Folge hat. An atmosphere with a CO to H 2 ratio of 1: 1 is thus achieved, that is to say the optimum ratio for carburization, which results in a maximum carbon transition number β.

Die üblicherweise durch CH4 oder C3H8 erreichte Anreicherung bzw. Abreaktion des beim Aufkohlungsprozeß entstehenden Wassers und Kohlendioxids wird erfindungsgemäß durch Verstellung des stöchiometrischen Verhältnisses von Äthanol und Kohlendioxid erreicht, denn bei einem Überangebot von Äthanol entsteht gemäß 2 C2H5OH + 1 CO2 ---> CH4 + 2 CO + 2 CO + 4 H2 auch ein Methananteil im Produktgas, der die Aufgabe des sonst eigenständig zugeführten Anreicherungsgases übernimmt. Die Bereitstellung eines Anreicherungsgases entfällt daher beim erfindungsgemäßen Verfahren. Im übrigen entsteht selbst bei unabgestimmtem stöchiometrischem Verhältnis ein Atmosphärengas mit einem CO-zu-H2-Verhältnis von exakt 1:1, das vor allem einer beschleunigten Aufkohlung dient.The accumulation or reaction of the water and carbon dioxide formed during the carburizing process, which is usually achieved by CH 4 or C 3 H 8 , is achieved according to the invention by adjusting the stoichiometric ratio of ethanol and carbon dioxide, because if there is an excess supply of ethanol, 2 C 2 H 5 OH + 1 CO 2 ---> CH 4 + 2 CO + 2 CO + 4 H 2 also a methane content in the product gas, which takes over the task of the enrichment gas, which is otherwise supplied independently. The preparation of an enrichment gas is therefore not necessary in the method according to the invention. Incidentally, even with an unadjusted stoichiometric ratio, an atmospheric gas with a CO to H 2 ratio of exactly 1: 1 is produced, which primarily serves to accelerate carburization.

Hinzu kommt, daß das Äthanol-Kohlendioxid-System hinsichtlich seiner Reaktionseigenschaften günstige Verhältnisse bietet. Es reagiert nämlich bereits bei etwa 800°C in gewünschter Weise und Äthanol und Kohlendioxid können daher - gemäß einer bevorzugten Verfahrensvariante - zur Atmosphärenbildung ohne weitere Maßnahmen direkt in einen Aufkohlungsofen eingebracht werden. Eine Verfahrensweise mit einem eigenständigen Atmosphären-Generator kann jedoch dennoch in einigen Einsatzfällen erforderlich sein.In addition, the ethanol-carbon dioxide system with regard to its reaction properties offers favorable conditions. It already reacts at about 800 ° C in the desired way and ethanol and carbon dioxide can therefore - according a preferred process variant - for atmospheric formation without further measures directly into a carburizing furnace. A procedure with a standalone atmosphere generator can still work in some Applications may be required.

Mit dem System "Äthanol und Kohlendioxid" ergibt sich femer ein Zweikomponentensystem, das vergleichsweise einfach regelbar ist. In einer vorteilhaften Ausgestaltung wird derart verfahren, daß der Kohlenstoffpegel im Aufkohlungsofen fortlaufend gemessen wird und die Verstellung des stöchiometrischen Verhältnisses von Äthanol und Kohlendioxid entsprechend dem gewünschten Kohlenstoffpegel verändert wird. Insbesondere ist es vorteilhaft, wenn bei der Ausgestaltung der erfindungsgemäßen Atmosphärenbildung immer eine Komponente konstant in die Anlage gespeist wird, und die andere, abhängig von einer Kohlenstoffpegelmessung, geregelt zugeleitet wird.The "ethanol and carbon dioxide" system also results in a two-component system, that is comparatively easy to regulate. In an advantageous embodiment The procedure is such that the carbon level in the carburizing furnace is measured continuously and the adjustment of the stoichiometric ratio of ethanol and changing carbon dioxide according to the desired carbon level. In particular, it is advantageous if when designing the invention Atmospheric formation, one component is constantly fed into the system, and the other, depending on a carbon level measurement, supplied in a controlled manner becomes.

Eine Aufkohlungsanlage gemäß der Erfindung ist im Patentanspruch 1 angegeben und ist dadurch gekennzeichnet, daß der zugehörige Aufkohlungsofen zum Zweck der Atmosphärenbildung sich ausschließlich einer Äthanolquelle (A) und einer Kohlendioxidquelle (C) bedient und demzufolge mit diesen verbunden ist, und daß ein Meßgerät (M) zur Messung des Kohlenstoffpegels im Ofen vorhanden ist, das seinerseits mit einer Mengensteuereinheit in der Äthanolzuleitung und/oder der Kohlendioxidzuleitung verbunden ist.A carburizing plant according to the invention is specified in claim 1 and is characterized in that the associated carburizing furnace for the purpose of atmosphere formation only an ethanol source (A) and a carbon dioxide source (C) served and therefore with this is connected, and that a measuring device (M) for measuring the carbon level is present in the furnace, which in turn has a quantity control unit in the ethanol feed line and / or the carbon dioxide feed line is connected.

Im folgenden wird die Erfindung in Verbindung mit der anliegenden Figur anhand eines Ausführungsbeispiels näher erläutert. Die Figur zeigt eine Anlagengestaltung gemäß der Erfindung mit geregelter CO2-Zuführung.The invention is explained in more detail below in connection with the attached figure using an exemplary embodiment. The figure shows a system design according to the invention with regulated CO 2 supply.

Ein Aufkohlungsofen O ist zunächst mit einer Äthanolquelle A und mit einer Kohlendioxidquelle C über geeignete Leitungen und Stellglieder zu koppeln. Die Äthanolversorgung besteht aus einer Äthanolpumpe P und einer Leitung 1, die vor Erreichen des Aufkohlungsofens in eine Verdüsungseinheit V einmündet. Ebenso in die Verdüsungseinheit mündet eine Kohlendioxidzuleitung 2d. Die Kohlendioxidzuleitung 2d teilt sich stromaufwärts der Verdüsungseinheit V in einen Parallelschaltungsabschnitt mit zwei Leitungen 2b und 2c auf, in denen jeweils ein Stellglied - S1 und S2 - zur Mengenregelung vorhanden ist. Schließlich ist die Parallelschaltung über einen Leitungsabschnitt 2a und ein Hauptventil H mit der CO2-Quelle C verbunden. Femer ist ein Flußmengenmesser FIC im Leitungsabschnitt 2a vorhanden. Darüber hinaus ist der Aufkohlungsofen O mit einem Meßgerät M zur Messung des Kohlenstoffpegels in seinem Innenraum ausgestattet. Das Meßgerät M wiederum ist mit einem Steuergerät S verbunden, das seinerseits auf das Stellglied S2 in der Bypassleitung 2c der Parallelschaltung einwirkt.A carburizing furnace O is first to be coupled to an ethanol source A and to a carbon dioxide source C via suitable lines and actuators. The ethanol supply consists of an ethanol pump P and a line 1, which opens into a atomization unit V before reaching the carburizing furnace. A carbon dioxide feed line 2d likewise opens into the atomization unit. The carbon dioxide feed line 2d divides upstream of the atomization unit V into a parallel circuit section with two lines 2b and 2c, in each of which an actuator - S1 and S2 - is provided for quantity control. Finally, the parallel connection is connected to the CO 2 source C via a line section 2a and a main valve H. There is also a flow meter FIC in line section 2a. In addition, the carburizing furnace O is equipped with a measuring device M for measuring the carbon level in its interior. The measuring device M in turn is connected to a control device S, which in turn acts on the actuator S2 in the bypass line 2c of the parallel connection.

Eine erfindungsgemäße Verfahrensweise dieser Anlage besteht darin, daß in den auf Temperatur befindlichen Ofen O die Ausgangsmedien Äthanol und Kohlendioxid in bestimmten Basisquantitäten eingeleitet werden, die durch geeignete Einstellung der Pumpleistung der Äthanolpumpe P sowie des Stellglieds S1 festgelegt werden. Grundsätzlich sind die Zuleitungsmengen etwa so einzustellen, daß ein Mol Äthanol auf ein Mol CO2 kommt, wobei in der gezeigten Variante grundsätzlich ein Äthanolüberschuß vorzusehen ist. Im Ofen bei über 800°C entsteht aus diesen Ausgangsmedien eine, im wesentlichen im Verhältnis 1:1 CO und H2 enthaltende, Atmosphäre, deren Kohlenstoffpegel durch das Meßgerät M, beispielsweise eine Sauerstoffsonde oder eine C-Strom-Sonde, ermittelt wird. Da im beschriebenen Fall im Grundsatz mit einem Äthanolüberschuß gefahren wird, entsteht ein relativ hoher C-Pegel in der Grundeinstellung der Anlage. Wird daher vom Meßgerät ein den gewünschten C-Pegel übersteigender Wert ermittelt, so wird durch das entsprechend programmierte Steuergerät S das Öffnen des Stellglieds S2 ausgelöst, und damit die CO2-Zufuhr erhöht. In der Folge sinkt der C-Pegel bis, bei Erreichen einer festzulegenden Untergrenze, das Stellglied S2 wieder geschlossen wird. Auf diese Weise wird eine relativ einfache, extrem effiziente, C-Pegel-geregelte Aufkohlungsatmosphäre erhalten.A procedure according to the invention of this system is that the starting media ethanol and carbon dioxide are introduced in certain basic quantities into the furnace O which is at a temperature and which are determined by suitable adjustment of the pumping power of the ethanol pump P and of the actuator S1. Basically, the feed quantities are to be adjusted so that one mole of ethanol comes to one mole of CO 2 , with an excess of ethanol generally being provided in the variant shown. In the furnace at more than 800 ° C, an atmosphere is obtained from these starting media, essentially containing 1: 1 CO and H 2 , the carbon level of which is determined by the measuring device M, for example an oxygen probe or a C-flow probe. Since in the described case, in principle an excess of ethanol is used, a relatively high C level arises in the basic setting of the system. If a value exceeding the desired C level is therefore determined by the measuring device, the correspondingly programmed control device S triggers the opening of the actuator S2 and thus increases the CO 2 supply. As a result, the C level drops until, when a lower limit to be defined is reached, actuator S2 is closed again. In this way, a relatively simple, extremely efficient, C-level controlled carburizing atmosphere is obtained.

Claims (5)

  1. Process for carburizing metallic workpieces in a furnace at high temperatures and in an atmosphere which contains CO and H2, in which the atmosphere is formed by reacting an oxygen-containing hydrocarbon medium, in particular an alcohol, with carbon dioxide, characterized in that the atmosphere is formed on the basis of ethanol and carbon dioxide, and the enrichment or depletion of the atmosphere, i.e. the setting of a defined carbon level, is achieved by suitable adjustment of the stoichiometric ratio of ethanol and carbon dioxide.
  2. Process according to Claim 1, characterized in that to form the atmosphere ethanol and carbon dioxide are introduced directly into a carburization furnace at working temperature.
  3. Process according to Claim 1 or 2, characterized in that the carbon level in the carburization furnace is measured continuously and the adjustment of the stoichiometric ratio of ethanol and carbon dioxide is altered according to the desired carbon level.
  4. Process according to Claim 3, characterized in that one component used to form the atmosphere is supplied at a constant level and the supply of the other component used to form the atmosphere is regulated as a function of the carbon level measurement in the carburization furnace.
  5. Carburizing installation, characterized in that the associated carburization furnace uses only an ethanol source (A) and a carbon dioxide source (C) to form the atmosphere and consequently is connected to these sources,
    the ethanol supply comprising an ethanol pump (P), which is connected to the ethanol source (A), and a line (1) which is connected to the ethanol pump and, before it reaches the carburization furnace, opens out into an atomizing unit (V), which is connected to the furnace and into which a carbon dioxide feed line (2d) which is coupled to the carbon dioxide source (C) also opens out,
    and in which there is a measuring unit (M) for measuring the carbon level in the furnace, which unit, for its part, is connected to a quantity control unit (S), which can act on the quantitative flow through the ethanol feed line and/or through the carbon dioxide feed line.
EP99108094A 1998-04-28 1999-04-23 Process and apparatus for gas carburising Expired - Lifetime EP0953654B1 (en)

Applications Claiming Priority (2)

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DE19819042 1998-04-28
DE19819042A DE19819042A1 (en) 1998-04-28 1998-04-28 Process and plant for gas carburizing

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EP0953654A1 EP0953654A1 (en) 1999-11-03
EP0953654B1 true EP0953654B1 (en) 2003-09-17

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Publication number Priority date Publication date Assignee Title
FR2939448B1 (en) * 2008-12-09 2011-05-06 Air Liquide PROCESS FOR PRODUCING A GAS ATMOSPHERE FOR PROCESSING METALS

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4317687A (en) * 1980-05-12 1982-03-02 Air Products And Chemicals, Inc. Carburizing process utilizing atmospheres generated from nitrogen-ethanol based mixtures
DE3224607A1 (en) * 1982-07-01 1984-01-05 Linde Ag, 6200 Wiesbaden Method for the case-hardening and neutral-carburising annealing of metal workpieces
KR910004557B1 (en) * 1986-08-12 1991-07-06 미쯔비시지도오샤 고오교오 가부시기가이샤 Gas carburizing method and apparatus
DE4340060C1 (en) * 1993-11-24 1995-04-20 Linde Ag Process for gas carburising
JP3409236B2 (en) * 1997-02-18 2003-05-26 同和鉱業株式会社 Atmosphere control method of heat treatment furnace

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EP0953654A1 (en) 1999-11-03
ATE250153T1 (en) 2003-10-15
DE19819042A1 (en) 1999-11-04
DE59906984D1 (en) 2003-10-23

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